Last winter, Dante de Kort — an eight-year-old boy who lives in central Arizona — found a dead collared peccary, a wild pig-like animal, near his house. He set up a motion-controlled camera nearby, and over the next ten days, was surprised to discover footage of the peccary’s herd returning to visit their dead herd-member, over and over.

When he wrote up his findings in a school science-fair presentation, it caught the attention of local biologist Mariana Altricher. It looked like the wild pecarries were in mourning, which was surprising: Scientists have seen grief-like behavior in animals like elephants, dolphins and primates, which are known for their high level of intelligence. But never in these creatures, as National Geographic reports:

Having studied the social, pig-like mammals for years, Altrichter knew how tightly bonded peccaries could be. But she’d never witnessed herd members return to a body repeatedly …

“It was pretty amazing because it wasn’t just an immediate reaction and then they moved on—it went on for 10 days,” says Altrichter, chair of the International Union for Conservation of Nature’s Peccary Specialist Group. [snip]

In the videos, the peccaries pay close attention to the body, nuzzling, biting, sniffing, and staring at it. They slept next to the carcass, and even tried to lift it by wedging their snouts under the body and pushing upward.

And when a pack of coyotes approached their fallen peer, the herd chased them away. “It really surprised me that they would stand up to the coyotes,” says de Kort, noting the peccaries were outnumbered.